An integrated circuit (“IC”) is a semiconductor device that includes many electronic components (e.g., transistors, diodes, inverters, etc.). These electrical components are interconnected to form larger scale circuit components (e.g., gates, cells, memory units, arithmetic units, controllers, decoders, etc.) on the IC. The electronic and circuit components of IC's are jointly referred to below as “components.” An integrated circuit also includes multiple layers of metal and/or polysilicon wiring that interconnect its electronic and circuit components.
Design engineers create an integrated circuit by transforming a circuit description of the integrated circuit into a geometric description called a “layout”. To create an integrated circuit layout, design engineers typically use electronic design automation (“EDA”) applications. These EDA applications provide sets of computer-based tools for creating, editing, and analyzing IC design layouts. EDA applications create layouts by using geometric shapes that represent different materials and devices on integrated circuits. For instance, EDA tools commonly use rectangular lines to represent the wire segments that interconnect the various IC components. These EDA tools also represent electronic and circuit IC components as geometric objects with varying shapes and sizes. For the sake of simplifying the discussion, these geometric objects are shown as rectangular blocks in this document. Also, in this document, the geometric representation of an electronic or circuit IC component by an EDA application is referred to as a “circuit module.”
EDA applications typically illustrate circuit modules with electrical interface “pins” on the sides of the circuit modules. These pins connect to the interconnect lines, the “wiring” used to connect the various circuit modules in the integrated circuit. A collection of pins that are, or need to be, electrically connected is referred to as a “net”.
Many integrated circuits are currently fabricated with five metal layers for interconnecting circuit modules. In theory, the wiring on the metal layers can be all-angle wiring (i.e., the wiring can be in any arbitrary direction). Such all-angle wiring is commonly referred to as Euclidean wiring. In practice, however, each metal layer typically has a preferred wiring direction in an attempt to maximize the number of signal wires that may be placed on each wiring layer by preventing intersections. In current integrated circuits, the preferred direction alternates between successive metal layers. Most integrated circuits use a “Manhattan” wiring model, which specifies alternating layers of preferred-direction horizontal and vertical wiring. (Viewed from above, the horizontal and vertical interconnect wires of the integrated circuit resemble the orthogonal streets of Manhattan.) In the Manhattan wiring model, essentially all of the interconnect wires are horizontal or vertical.
The Manhattan wiring model has proven to be useful, but it is certainly not optimal. Diagonally separated distant pins must often be connected by long stretches of connected horizontal and vertical interconnect signals. To provide a more optimal system, a related patent application title “Multi-Directional Wiring On A Single Metal Layer”, filed on Dec. 12, 2000 and having Ser. No. 09/733,104, now U.S. Pat. No. 6,858,928 incorporated by reference, uses a non Manhattan wiring model that uses diagonal direction wiring as a “preferred” direction for some of the wiring layers. Using diagonal wiring allows two diagonally separated pins to be connected with a shorter diagonal wire. For purposes of nomenclature, a “preferred” direction is defined as the direction that at least 40 percent of the wires are configured. Interconnect lines are considered “diagonal” if they form an angle other than zero or ninety degrees with respect to the layout boundary of the integrated circuit.
Although the introduction of the non Manhattan wiring architecture allows integrated circuits to be wired with greater efficiency, the non Manhattan wiring architecture requires a whole new set of electronic design automation (“EDA”) applications. Existing EDA applications have been created with the premise that all interconnect wiring will be horizontal or vertical. Thus, a new set of EDA applications that have been designed with the premise of diagonal wiring are needed to take advantage of the inherent efficiencies of diagonally wired integrated circuits.